Lesser Scaup

Aythya affinis
STANFORD LOCATIONS:

Uncommon winter visitor in more open, deeper water at Lagunita.
  
Nest
Location
Nest
Type
Eggs
Mating System
Dev.
Parental Care
Primary &
2ndary Diet
Foraging
Strategy
F
I: 21-28 DAYS
PRECOCIAL 2
F
9-12
(8-14)
MONOG
F: 45-50 DAYS
F
AQUATIC
PLANTS
BREEDING: Often upland areas near pond or small lake, marsh, prairie potholes. 1 brood.
DISPLAYS: See: Duck Displays.
NEST: In fairly open, dry habitat within 150' of water, nest concealed by veg, rarely over water. Lined with grass, down; uses less down in nest than do other ducks. Built as eggs are laid.
EGGS: Olive/olive-buff. 2.3" (57 mm).
DIET: Aquatic invertebrates, esp amphipods; aquatic veg.
CONSERVATION: Winters s throughout C.A. and West Indies to n S.A.
NOTES: Male deserts when incubation begins, occ remains until middle of incubation. Young led to water; if disturbed, dive and disperse. Young form crèches, several broods often combined and tended by 1-3 females. Nests holding >14 eggs are due to >1 female laying in nest. Clutch size increases with age of female; nest success of females >2 years old is greater than that of 1- and 2-year-old females. Occ feeds at night. Large winter flocks, occ with Greater Scaup.
ESSAYS: Eye Color; Bird Communities and Competition; Metallic Poisons; Dabblers vs. Divers; Crèches; Parasitized Ducks; Variation in Clutch Sizes.
REFERENCES: Afton, 1984; Bellrose, 1976; Gooders and Boyer, 1986.

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Except for Stanford Locations, the material in this species treatment is taken, with permission, from The Birder's Handbook (Paul Ehrlich, David Dobkin, & Darryl Wheye, Simon & Schuster, NY. 1988).